[[ RefactorGraphics ]] switch return type of MCMacStackSurface::LockGraphics(…) to MCGContextRef
[[ RefactorGraphics ]] Implement MCMacStackSurface methods Lock() & Unlock()
Merge branch 'refactor-graphics' of https://github.com/runrev/livecode into refactor-graphics
[[ RefactorGraphics ]] Update CoreImage transitions to use MCGImage, MCStackSurface